Various types of latching mechanisms have been developed for mounting and/or locking aircraft panels, such as engine cowlings, to one another or to an aircraft structure. Many of these standard latching mechanisms employ a keeper, a hook to engage the keeper, a mounting linkage for mounting the hook to the aircraft structure, and a handle to actuate the latch through the mounting linkage. In such devices, overcenter locking mechanisms associated with the mounting linkage establish rigid retention of the aircraft panel with the latch and the corresponding aircraft panel or structure in the closed state. The handle controls the overcenter mechanism and is itself independently latched into place in the closed position.
Overcenter latching mechanisms are often used for securing engine cowlings to an aircraft structure. An engine cowling usually forms a conical shaped structure that wraps around an aircraft engine. Engine cowlings at their top ends are normally hingedly connected to the aircraft structure so that they can be pivoted upwards to provides access to the engine for maintenance or repair. During aircraft operation the engine cowlings must be pivoted downwards into closed positions and secured at their bottom ends to the aircraft structure by latching mechanisms.
A disadvantage of using standard overcenter latching mechanisms for securing a cowling to an aircraft structure is that these latches require a complete manual closing. For example, a persistent problem associated with helicopter cowlings occurs after the required maintenance or repair is performed on the helicopter engines. Mechanics will pivot the cowling downwards but will sometimes forget to close the overcenter latch or will not close the overcenter latch completely. Oftentimes, this is because the mechanics are in a hurry to return the helicopter to operation. When these overcenter latches are not completely closed a potentially unsafe flight condition may occur. For example, the cowling could possibly open into the blades of the helicopter.
Another type of latch designed for securing aircraft cowlings is described in U.S. Pat. No. 3,515,421 to Poe and Brockway. This patent describes a latch with a pair of opposed pivotally connected keeper jaws which move longitudinally in a housing between an open position to receive and release a keeper pin, a pre-catch position yieldable to pressure exerted by the keeper pin to receive and retain the keeper pin, and a closed position for securing the keeper pin. The keeper jaws of this latch are manipulated by a transversely extending slide containing a stepped slot which operates laterally with respect to the direction of movement of the keeper jaws and the keeper pin. The transversely extending slide extends through the housing. After the opposed jaw latch is opened the latch will automatically bias to the pre-catch position. From the pre-catch position, the opposed jaw latch can be closed by the use of a handle or by the slamming of the cowling to its closed position. The pre-catch position of this latch provides a safety feature such that when the cowling is pivoted downward the keeper jaws may yield to the pressure exerted by the keeper pin and the latch may accept and retain the keeper pin between the keeper jaws. Therefore, if the mechanic forgets to manually close the opposed jaw latch, the jaws may still accept and retain the keeper pin during flight possibly obviating a potentially unsafe flight condition due to the cowling opening during flight. Although this type of latch has been used previously with aircraft, the opposed jaw latch has many disadvantages.
A disadvantage of the opposed jaw latch is that it operates laterally by means of a transversely extending slide containing a stepped slot which extends through the housing making the opposed jaw latch prone to open from its closed and pre-catch positions. Disadvantageously, the laterally operable slide is very susceptible to forces encountered during flight and is inherently unstable. The slide is likely to move in reaction to these forces which may cause the opposed jaw latch to open from the closed position. Similarly, the lateral operation of the slide makes the opposed jaw latch prone to open from the pre-catch position as well. From both the closed and the pre-catch positions, the opposed jaw latch is prone to open, possibly allowing the cowling to pivot upwards during flight.
A disadvantage of the opposed jaw latch, as well as the standard overcenter latches, is that if the keeper pin is missing, broken, or not in the proper position, it still may be possible to close the latch without properly engaging the keeper pin. As previously described, this may result in the cowling opening during flight. A further disadvantage associated with these latches, is that there is no way for the mechanic to visually verify whether or not these latches have properly closed, since the handles associated with these latches will still close regardless of whether the latches have correctly engaged the keeper pin. Therefore, the mechanic operating theses types of latches can never be sure that the latch has properly closed.
A further disadvantage of the opposed jaw latch is that in the closed position the jaws are loosely held in place by the housing. Since the jaws are loosely held in place by the housing, the opposed jaw latch does not adequately retain the keeper pin. Similarly, in the pre-catch position, the jaws of the opposed jaw latch do not adequately retain the keeper pin.
In view of the above, it should be appreciated that there is a need for an overcenter double jaw latch mechanism that provides the advantages of having a double jaw latch that is secure in the closed and pre-catch positions and not prone to inadvertently open, is inherently stable, prevents the latch from closing without properly engaging the keeper pin and alerts the mechanic of this condition by not allowing the handle to close, and has a housing that rigidly retains the keeper pin in the closed position and securely retains the keeper pin in the pre-catch position. The present invention satisfies these and other needs and provides further related advantages.